按二维对 NSArray 进行排序 - Objective-C

Question

从历史上看，这个排序工厂已经能够按一维对一组发票项目对象进行排序。各种排序维度作为 SortItem 对象的属性存储在枚举 "state" 中。这是工作实施。

+(NSArray *)SortInvoiceItems:(NSArray *)items forSort:(SortItem*)sortItem forSecondarySort:(SortItem*)secondarySortItem {
    NSArray * primary = [items sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
        InvoiceItems *iiA = (InvoiceItems *)a;
        InvoiceItems *iiB = (InvoiceItems *)b;
        switch(sortItem.state) {
            case DateAscending:
            case DateDescending: {
                return (sortItem.state == DateAscending) ? [iiA.transactionDate compare:iiB.transactionDate] : [iiB.transactionDate compare:iiA.transactionDate];
            }
            case SumDescending:
            case SumAscending: {
                return (sortItem.state == SumAscending) ? [iiA.netInvoiceAmount compare:iiB.netInvoiceAmount] : [iiB.netInvoiceAmount compare:iiA.netInvoiceAmount];
            }
            case UnitPriceDescending:
            case UnitPriceAscending: {
                return (sortItem.state == UnitPriceAscending) ? [iiA.uomNetAmt compare:iiB.uomNetAmt] : [iiB.uomNetAmt compare:iiA.uomNetAmt];
            }
            default:
                return 0;
        }
    }];

    return primary;
}

您会注意到我在未使用的方法签名中添加了一个 secondarySort 参数。我的objective是允许按这个次级维度排序，按这个次级维度对主维度有相同值的Invoice Item对象进行排序。

因此，如果两个项目具有相同的 .transactionDate，则这两个项目将另外按第二个维度排序，例如单价降序。

编辑：我让它在下面工作，有没有更简洁的方式来写这个？

+(NSArray *)SortInvoiceItems:(NSArray *)items forSort:(SortItem*)sortItem forSecondarySort:(SortItem*)secondarySortItem {

    NSSortDescriptor *primaryDescriptor;
    NSSortDescriptor *secondaryDescriptor;

    switch(sortItem.state) {
        case DateAscending:
            primaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"transactionDate" ascending:YES];
            break;
        case DateDescending:
            primaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"transactionDate" ascending:NO];
            break;
        case SumAscending:
            primaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"netInvoiceAmount" ascending:YES];
            break;
        case SumDescending:
            primaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"netInvoiceAmount" ascending:NO];
            break;
        case UnitPriceAscending:
            primaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"uomNetAmt" ascending:YES];
            break;
        case UnitPriceDescending:
            primaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"uomNetAmt" ascending:NO];
            break;
        default: NSLog(@"invalid sort item");
    }

    switch(secondarySortItem.state) {
        case DateAscending:
            secondaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"transactionDate" ascending:YES];
            break;
        case DateDescending:
            secondaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"transactionDate" ascending:NO];
            break;
        case SumAscending:
            secondaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"netInvoiceAmount" ascending:YES];
            break;
        case SumDescending:
            secondaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"netInvoiceAmount" ascending:NO];
            break;
        case UnitPriceAscending:
            secondaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"uomNetAmt" ascending:YES];
            break;
        case UnitPriceDescending:
            secondaryDescriptor = [[NSSortDescriptor alloc] initWithKey:@"uomNetAmt" ascending:NO];
            break;
        default: NSLog(@"invalid sort item");
    }

    NSArray *sortDescriptors = @[primaryDescriptor, secondaryDescriptor];
    return [items sortedArrayUsingDescriptors:sortDescriptors];
}

第二次编辑：重构为：

+(NSArray *)SortInvoiceItems:(NSArray *)items forPrimarySort:(SortItem*)primary forSecondarySort:(SortItem*)secondary {

    NSSortDescriptor *primaryDescriptor = [self GetDescriptorForSortItem:primary];
    NSSortDescriptor *secondaryDescriptor = [self GetDescriptorForSortItem:secondary];
    NSArray *sortDescriptors = @[primaryDescriptor, secondaryDescriptor];

    return [items sortedArrayUsingDescriptors:sortDescriptors];
}

+(NSSortDescriptor *)GetDescriptorForSortItem:(SortItem*)sortItem {
    switch(sortItem.state) {
        case DateAscending:
            return [[NSSortDescriptor alloc] initWithKey:kTransactionDateString ascending:YES];
        case DateDescending:
            return [[NSSortDescriptor alloc] initWithKey:kTransactionDateString ascending:NO];
        case SumAscending:
            return [[NSSortDescriptor alloc] initWithKey:kNetInvoiceAmount ascending:YES];
        case SumDescending:
            return [[NSSortDescriptor alloc] initWithKey:kNetInvoiceAmount ascending:NO];
        case UnitPriceAscending:
            return [[NSSortDescriptor alloc] initWithKey:kUOMNetAmount ascending:YES];
        case UnitPriceDescending:
            return [[NSSortDescriptor alloc] initWithKey:kUOMNetAmount ascending:NO];
        default:
            return [[NSSortDescriptor alloc] initWithKey:kTransactionDateString ascending:NO]; // default to date descending
    }
}

Answer 1

使用NSArray的-sortedArrayUsingDescriptors:来解决这个问题。使用此方法，您可以提供一个 NSSortDescriptor 数组，其中第二个将用作二级排序（如果有第三个，它将是三级排序等）。

您可以使用 -[NSSortDescriptor initWithKey:ascending:comparator:] 创建一个 NSSortDescriptor 并传递比较器块。

Answer 2

使用 NSSortDescriptor 构建排序，如此处解释：https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/SortDescriptors/Articles/Creating.html

编辑：在您的情况下，由于您有一个名为 state 的 SortItem 属性来确定排序描述符，并且由于您有能力根据需要构造 state 类型，所以我建议您使排序描述符成为状态本身的一部分。这样，当需要排序时，没有工作要做：状态本身提供您将使用的排序描述符，您可以摆脱 SortInvoiceItems 中的开关。一般来说，开关可以看作是一种不好的气味，表明你没有正确设计你的对象类型；您应该让实际对象知道该做什么，而不是打开某些东西。

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